22Mn13Cr5Ni鋼の4Kでの破壊靱性値に及ぼす予亀裂導入温度と荷重の影響
1988 年 23 巻 5 号 p. 261-267
詳細
1988 年 23 巻 5 号 p. 261-267
Effects of precracking temperatures and load on 4K fracture toughness, KIC, of tough 22Mn13Cr5Ni steel were investigated using an unloading compliance method. Compact tension specimens with a thickness of 25mm were precracked by fatigue at 298K, 77K and 4K. The stress intensity factor range, ΔKf, covered from 20 to 60MPa√m. The main results are as follows; (1) The experimental results showed that precracking temperatures and ΔKf hardly affected 4K-KIC of the 22Mn13Cr5Ni steel. (2) No α′ martensite was induced by precracking at all but ε martensite was induced at 4K. A subcritical crack growth started with a fracture of induced ε in 4K fracture toughness test. The dominant ε was not one induced by precracking but by fracture toughness test itself. Therefore the effects of ε by precracking at cryogenic temperature could be neglected. (3) Room temperature precracking produced a larger plastic zone than law temperatures. However its effect on 4K-KIC was very small because contraction of plastic zone could be expected and because ε was not induced at all.
